docs: def _get_error_message(self, model_class, method_name, action_method_name):
          """
          Get assertion error message depending if there are actions permissions methods defined.
          """
          if action_method_name:
              return "'{}' does not have '{}' or '{}' defined.".format(model_class, method_name, action_method_name)
          else:
              return "'{}' does not have '{}' defined.".format(model_class, method_name)